i want to upgrade my valvetrain w/ a cc306, 1.5-1.6 rr's new pushrods, lifters, valve springs and retainers and a heavy duty timing set. i know this adds a lot of power to the car, but if im using stock heads i know i won't get the full power out of the setup until i upgrade those as well. what i want to know is it going to affect the stock heads if i run this power setup w/ them or can they stay on w/ a good tune and not get messed up in any way.

 

It won't mess them up at all, you just won't make all the HP you can with ported heads.